Undecideds: the kingmakers in France's election

Eleven candidates are running in France's 2017 presidential election, which will hold its first round on April 23, 2017

They are potentially the kingmakers in the first round of France's hard-fought presidential election, but they still haven't made up their minds -- even though voting is just hours away.

"I don't like any of them, they're all disappointing, said 73-year-old Ghislaine Pincont, a pensioner in the northern city of Lille. "At worst, I'll cast a blank vote."

She is among around 25 percent of France's electorate still on the fence ahead of Sunday's poll, which is the most unpredictable in decades.

While that percentage of undecideds is in line with previous elections, the unprecedented four-way race has made even relatively small rushes of support crucial to victory.

In the final polling before a pre-election blackout mandated under French law, the main candidates were locked in a battle within about four points of each other.

The two top vote-getters on Sunday will go on to battle for the presidency in a May 7 run-off.

Undecided voters told AFP they were struggling to pick among a field of candidates whom they thought were all flawed in some way.

"I've already decided against some of them... all the extremes, all the smaller, slightly quirky candidates," Aude Remy, 43, who works in logistics, told AFP in the southeast city of Lyon.

Two of the four main contenders are arch-eurosceptics -- far-right leader Marine Le Pen, 48, and left-wing firebrand Jean-Luc Melenchon, 65 -- who have promised to completely alter France's relationship within the European Union.

- 'Daily' terror threat -

Le Pen has positioned herself as a protector of French interests in a globalised world, but her anti-immigrant, anti-EU platform has generated worries about the future of France and the bloc.

A business owner in the southwest city of Toulouse, 41-year-old Tarik Boudra, said he had whittled the field down to Melenchon and conservative ex-prime minister Francois Fillon, but was still hesitating.

"Fillon is the one with the most experience. What also attracts me to him is lower taxes, which is important in business," he added.

But Fillon, once tipped to win, saw his hopes severely dented by the so-called "fake jobs" scandal, in which he stands accused of paying his wife hundreds of thousands of euros in public funds in return for very little work.

He has since rebounded, but remains behind frontrunners Le Pen and centrist Emmanuel Macron, a 39-year-old ex-banker who rose in the polls despite never holding elected office.

"It's going to come down to personality because in any case they will make promises, but won't keep them," said 31-year-old Elodie Grange in Lyon.

Macron has battled criticism that he lacks substance and serves as a blank canvas for voters seduced by his pro-reform, pro-Europe platform.

Another voter, 40-year-old Julie Varin from the eastern Jura region, said she would cast a ballot -- though not because the candidates had her fired up "but out of respect for democracy, for all the countries where people don't have the right to vote," she said.

Candidates' platforms and experience will determine who gets her vote, while the threat of terrorism, "which is sadly becoming part of daily life, doesn't make me feel unsafe because I'm not in Paris," said Varin, a teacher.

Pincont, the Lille pensioner, agreed, pointing to the jihadist killing of a policeman on Thursday on Paris's Champs Elysees that thrust security to the election's forefront.

"In any case the attack on the Champs Elysees won't have any impact on my choice," she said.